1. Field of the Invention
The present invention relates to a thin-film magnetic head comprising at least an induction-type magnetic transducer and a method of manufacturing such a thin-film magnetic head.
2. Description of the Related Art
Performance improvements in thin-film magnetic heads have been sought as surface recording density of hard disk drives has increased. Composite thin-film magnetic heads have been widely used. A composite head is made of a layered structure including a recording head having an induction-type magnetic transducer for writing and a reproducing head having a magnetoresistive (MR) element for reading. MR elements include an anisotropic magnetoresistive (AMR) element that utilizes the AMR effect and a giant magnetoresistive (GMR) element that utilizes the GMR effect. A reproducing head using an AMR element is called an AMR head or simply an MR head. A reproducing head using a GMR element is called a GMR head. An AMR head is used as a reproducing head whose surface recording density is more than 1 gigabit per square inch. A GMR head is used as a reproducing head whose surface recording density is more than 3 gigabits per square inch.
The performance of the reproducing head is improved by replacing the AMR film with a GMR film and the like with an excellent magnetoresistive sensitivity. Alternatively, a pattern width such as an MR height, in particular, may be optimized. The MR height is the length (height) between an end of the MR element closer to the air bearing surface and the other end. The MR height is controlled by an amount of lapping when the air bearing surface is processed. The air bearing surface is a surface of the thin-film magnetic head facing toward a magnetic recording medium and may be called a track surface, too.
Performance improvements in a recording head are also required as the performance of a reproducing head is improved. One of the factors that determine the recording head performance is a pattern width such as a throat height (TH), in particular. The throat height is the length (height) of portions of magnetic pole layers facing each other with a recording gap layer in between, between the air-bearing-surface-side end and the other end. A reduction in throat height is desired in order to improve the recording head performance. The throat height is controlled as well by an amount of lapping when the air bearing surface is processed.
It is required to increase the track density on a magnetic recording medium in order to increase recording density among the performance characteristics of a recording head. To achieve this, it is required to implement a recording head of a narrow track structure wherein the width of top and bottom poles sandwiching the recording gap layer on a side of the air bearing surface is reduced down to a submicron order. Semiconductor process techniques are utilized to implement such a structure.
As thus described, it is important to fabricate well-balanced recording and reproducing heads to improve the performance of a thin-film magnetic head.
Reference is now made to FIG. 16A to FIG. 21A, FIG. 16B to FIG. 21B, and FIG. 22 to describe an example of a method of manufacturing a composite thin-film magnetic head as an example of a related-art method of manufacturing a thin-film magnetic head. FIG. 16A to FIG. 21A are cross sections each orthogonal to the air bearing surface of the thin-film magnetic head. FIG. 16B to FIG. 21B are cross sections of a pole portion of the head each parallel to the air bearing surface.
In the manufacturing method, as shown in FIG. 16A and FIG. 16B, an insulating layer 102 made of alumina (Al2O3), for example, having a thickness of about 5 to 10 xcexcm is deposited on a substrate 101 made of aluminum oxide and titanium carbide (Al2O3xe2x80x94TiC), for example. On the insulating layer 102 a bottom shield layer 103 made of a magnetic material is formed for making a reproducing head.
Next, as shown in FIG. 17A and FIG. 17B, on the bottom shield layer 103, alumina, for example, is deposited to a thickness of 100 to 200 nm through sputtering to form a bottom shield gap film 104 as an insulating layer. On the bottom shield gap film 104 an MR film having a thickness of tens of nanometers is formed for making an MR element 105 for reproduction. Next, on the MR film a photoresist pattern is selectively formed where the MR element 105 is to be formed. The photoresist pattern is formed into a shape that facilitates lift-off, such as a shape having a T-shaped cross section. Next, with the photoresist pattern as a mask, the MR film is etched through ion milling, for example, to form the MR element 105. The MR element 105 may be either a GMR element or an AMR element. Next, on the bottom shield gap film 104, a pair of electrode layers 106 are formed, using the photoresist pattern as a mask. The electrode layers 106 are electrically connected to the MR element 105.
Next, a top shield gap film 107 is formed as an insulating layer on the bottom shield gap film 104 and the MR element 105. The MR element 105 is embedded in the shield gap films 104 and 107.
Next, on the top shield gap film 107, a top-shield-layer-cum-bottom-pole-layer (called a bottom pole layer in the following description) 108 having a thickness of about 3 xcexcm is formed. The bottom pole layer 108 is made of a magnetic material and used for both a reproducing head and a recording head. Next, on the bottom pole layer 108, a recording gap layer 109 made of an insulating film such as an alumina film whose thickness is 0.2 xcexcm is formed.
Next, as shown in FIG. 18A and FIG. 18B, a portion of the recording gap layer 109 is etched to form a contact hole 119a to make a magnetic path. On the recording gap layer 109 in the pole portion, a top pole tip 110 made of a magnetic material such as Permalloy (NiFe) or FeN as a high saturation flux density material and having a thickness of 0.5 to 1.0 xcexcm is formed for the recording head. At the same time, a magnetic layer 119 made of a magnetic material is formed for making the magnetic path in the contact hole 109a for making the magnetic path.
Next, as shown in FIG. 19A and FIG. 19B, the recording gap layer 109 and the bottom pole layer 108 are etched through ion milling, using the top pole tip 110 as a mask. As shown in FIG. 19B, the structure is called a trim structure wherein the sidewalls of the top pole (the top pole tip 110), the recording gap layer 109, and part of the bottom pole layer 108 are formed vertically in a self-aligned manner. The trim structure suppresses an increase in the effective track width due to expansion of a magnetic flux generated during writing in a narrow track.
Next, an insulating layer 111 made of an alumina film, for example, and having a thickness of about 3 xcexcm is formed on the entire surface. The insulating layer 111 is then polished to the surfaces of the top pole tip 110 and the magnetic layer 119 and flattened. The polishing method may be mechanical polishing or chemical mechanical polishing (CMP). Through this polishing, the surfaces of the top pole tip 110 and the magnetic layer 119 are exposed.
Next, as shown in FIG. 20A and FIG. 20B, on the flattened insulating layer 111, a thin-film coil 112 of a first layer is made of copper (Cu), for example, for the induction-type recording head. Next, a photoresist layer 113 is formed into a specific pattern on the insulating layer 111 and the coil 112. Heat treatment is then performed to flatten the surface of the photoresist layer 113. On the photoresist layer 113, a thin-film coil 114 of a second layer is then formed. Next, a photoresist layer 115 is formed into a specific pattern on the photoresist layer 113 and the coil 114. Heat treatment is then performed to flatten the surface of the photoresist layer 115.
Next, as shown in FIG. 21A and FIG. 21B, a top pole layer 116 is formed for the recording head on the top pole tip 110, the photoresist layers 113 and 115, and the magnetic layer 119. The top pole layer 116 is made of a magnetic material such as Permalloy. Next, an overcoat layer 117 of alumina, for example, is formed to cover the top pole layer 116. Finally, machine processing of the slider is performed to form the air bearing surface 118 of the recording head and the reproducing head. The thin-film magnetic head is thus completed. FIG. 22 is a top view of the thin-film magnetic head. The overcoat layer 117 is omitted in FIG. 22.
In FIG. 21A and FIG. 21B, xe2x80x98THxe2x80x99 indicates the throat height and xe2x80x98MR-Hxe2x80x99 indicates the MR height. xe2x80x98P2Wxe2x80x99 indicates the pole width, that is, the recording track width. In addition to the throat height, the MR height and so on, the apex angle as indicated with xcex8 in FIG. 21A is one of the factors that determine the performance of a thin-film magnetic head. The apex is a hill-like raised portion of the coils covered with the photoresist layers 113 and 115. The apex angle is the angle formed between the top surface of the insulating layer 111 and the straight line drawn through the edges of the pole-side lateral walls of the apex.
With an increase in recording density of a hard disk drive used for computers and so on, the maximum frequency of data recorded or reproduced through the use of a thin-film magnetic head has increased. If the frequency of data to write increases, eddy current loss increases in the magnetic layers of an induction-type magnetic transducer. Accordingly, the following problems have arisen: a reduction in intensity of a write magnetic field generated from the pole portions opposed to each other with the gap layer in between; an increase in delay between a write current (a current responsive to data to write) supplied to the coil and generation of a write magnetic field; and a decrease in gradient of rise of a write magnetic field with respect to time. Those problems specifically manifest themselves in an increase in nonlinear transition shift (NLTS), for example.
In Published Unexamined Japanese Patent Application Hei 6-139521 (1994) and in Published Unexamined Japanese Patent Application Sho 60-35315 (1994), for example, related-art techniques to reduce eddy current loss in the magnetic layers and improve high frequency characteristics of the thin-film magnetic head are disclosed. In those techniques the magnetic layers making up the magnetic path of the induction-type magnetic transducer are made of alternating layers of soft-magnetic layers and insulating layers.
However, since the entire magnetic layers have such a layered structure in those techniques, the region through which a magnetic flux passes is narrow and the flux is prevented from passing. The amount of flux passing through the magnetic layers is thereby reduced.
Another technique disclosed in Published Unexamined Japanese Patent Application Hei 6-139521 provides a structure in which the magnetic layers making up the magnetic path of the induction-type magnetic transducer are made of alternating layers of soft-magnetic layers and insulating layers aligned along the direction orthogonal to the recording gap layer.
However, such a structure of the magnetic layers makes it difficult to maintain the direction of magnetization (magnetostriction) of the magnetic layers. It is therefore difficult to allow a magnetic flux to pass efficiently.
It is an object of the invention to provide a thin-film magnetic head and a method of manufacturing the same for reducing eddy current loss in magnetic layers making up a magnetic path of an induction-type magnetic transducer without preventing passage of a magnetic flux so as to improve high frequency characteristics.
A first thin-film magnetic head of the invention comprises: a first magnetic layer and a second magnetic layer magnetically coupled to each other and including magnetic pole portions opposed to each other and placed in regions of the magnetic layers on a side of a medium facing surface of the head that faces toward a recording medium, each of the magnetic layers including at least one layer; a gap layer provided between the pole portions of the first and second magnetic layers; and a thin-film coil at least part of which is placed between the first and second magnetic layers, the at least part of the coil being insulated from the first and second magnetic layers. Each of the first and second magnetic layers includes: a yoke portion connected to one of the pole portions and located in a region including a region that faces the coil. The yoke portion of at least one of the magnetic layers includes: a plurality of magnetic material layers; and a resistance layer located between adjacent two of the magnetic material layers and having an electric resistance greater than an electric resistance of the magnetic material layers. The resistance layer is located in a region of the yoke portion except a neighborhood of a portion connecting the yoke portion to one of the pole portion and except a neighborhood of a portion connecting the yoke portion to the other magnetic layer.
A first method of the invention is provided for manufacturing a thin-film magnetic head comprising: a first magnetic layer and a second magnetic layer magnetically coupled to each other and including magnetic pole portions opposed to each other and placed in regions of the magnetic layers on a side of a medium facing surface of the head that faces toward a recording medium, each of the magnetic layers including at least one layer; a gap layer provided between the pole portions of the first and second magnetic layers; and a thin-film coil at least part of which is placed between the first and second magnetic layers, the at least part of the coil being insulated from the first and second magnetic layers. Each of the first and second magnetic layers includes: a yoke portion connected to one of the pole portions and located in a region including a region that faces the coil. The method includes the steps of: forming the first magnetic layer; forming the gap layer on the first magnetic layer; forming the second magnetic layer on the gap layer; and forming the coil such that the at least part of the coil is placed between the first and second magnetic layers. In at least one of the steps of forming the first magnetic layer and forming the second magnetic layer, the yoke portion is formed to include: a plurality of magnetic material layers; and a resistance layer located between adjacent two of the magnetic material layers and having an electric resistance greater than an electric resistance of the magnetic material layers. The resistance layer is located in a region of the yoke portion except a neighborhood of a portion connecting the yoke portion to one of the pole portion and except a neighborhood of a portion connecting the yoke portion to the other magnetic layer.
According to the first thin-film magnetic head or the method of manufacturing the same of the invention, the yoke portion of at least one of the magnetic layers includes the plurality of magnetic material layers and the resistance layer. The resistance layer is located in a region of the yoke portion except a neighborhood of the portion connecting the yoke portion to the pole portion and except a neighborhood of the portion connecting the yoke portion to the other magnetic layer. As a result, it is possible to reduce eddy current loss in the magnetic layers without preventing the passage of a magnetic flux.
According to the first thin-film magnetic head or the method of manufacturing the same of the invention, the resistance layer may be divided and located in a plurality of separate regions.
According to the first head or method, the resistance layer may be made of an insulating material. In this case, the insulating material may be an inorganic material. According to the first method, the resistance layer may be formed into a specific pattern by selectively etching a layer of the inorganic material through reactive ion etching.
According to the first head or method, the first magnetic layer may include: a first portion located in a region including a region that faces the coil; and a second portion forming one of the pole portions and connected to a surface of the first portion that faces the coil. The at least part of the coil is located on a side of the second portion of the first magnetic layer. The yoke portion of the second magnetic layer includes the magnetic material layers and the resistance layer.
According to the first head or method, the head may further comprise: a magnetoresistive element; and a first shield layer and a second shield layer for shielding the magnetoresistive element, portions of the first and second shield layers located in regions on a side of the medium facing surface being opposed to each other, the magnetoresistive element being placed between the portions of the shield layers. In this case, the second shield layer may function as the first magnetic layer, too.
A second thin-film magnetic head of the invention comprises: a first magnetic layer and a second magnetic layer magnetically coupled to each other and including magnetic pole portions opposed to each other and placed in regions of the magnetic layers on a side of a medium facing surface of the head that faces toward a recording medium, each of the magnetic layers including at least one layer; a gap layer provided between the pole portions of the first and second magnetic layers; and a thin-film coil at least part of which is placed between the first and second magnetic layers, the at least part of the coil being insulated from the first and second magnetic layers. Each of the first and second magnetic layers includes: a yoke portion connected to one of the pole portions and located in a region including a region that faces the coil. The yoke portion of at least one of the magnetic layers includes: a plurality of magnetic material layers; and a resistance layer located between adjacent two of the magnetic material layers and having an electric resistance greater than an electric resistance of the magnetic material layers. The resistance layer is divided and located in a plurality of separate regions.
A second method of the invention is provided for manufacturing a thin-film magnetic head comprising: a first magnetic layer and a second magnetic layer magnetically coupled to each other and including magnetic pole portions opposed to each other and placed in regions of the magnetic layers on a side of a medium facing surface of the head that faces toward a recording medium, each of the magnetic layers including at least one layer; a gap layer provided between the pole portions of the first and second magnetic layers; and a thin-film coil at least part of which is placed between the first and second magnetic layers, the at least part of the coil being insulated from the first and second magnetic layers. Each of the first and second magnetic layers includes: a yoke portion connected to one of the pole portions and located in a region including a region that faces the coil. The method includes the steps of: forming the first magnetic layer; forming the gap layer on the first magnetic layer; forming the second magnetic layer on the gap layer; and forming the coil such that the at least part of the coil is placed between the first and second magnetic layers. In at least one of the steps of forming the first magnetic layer and forming the second magnetic layer, the yoke portion is formed to include: a plurality of magnetic material layers; and a resistance layer located between adjacent two of the magnetic material layers and having an electric resistance greater than an electric resistance of the magnetic material layers; and the resistance layer is divided and located in a plurality of separate regions.
According to the second thin-film magnetic head or the method of manufacturing the same of the invention, the yoke portion of at least one of the magnetic layers includes the plurality of magnetic material layers and the resistance layer. The resistance layer is divided and located in a plurality of separate regions. As a result, it is possible to reduce eddy current loss in the magnetic layers without preventing the passage of a magnetic flux.
According to the second head or method, the resistance layer may be made of an insulating material. In this case, the insulating material may be an inorganic material. According to the second method, the resistance layer may be formed into a specific pattern by selectively etching a layer of the inorganic material through reactive ion etching.
According to the second head or method, the first magnetic layer may include: a first portion located in a region including a region that faces the coil; and a second portion forming one of the pole portions and connected to a surface of the first portion that faces the coil. The at least part of the coil is located on a side of the second portion of the first magnetic layer. The yoke portion of the second magnetic layer includes the magnetic material layers and the resistance layer.
According to the second head or method, the head may further comprise: a magnetoresistive element; and a first shield layer and a second shield layer for shielding the magnetoresistive element, portions of the first and second shield layers located in regions on a side of the medium facing surface being opposed to each other, the magnetoresistive element being placed between the portions of the shield layers. In this case, the second shield layer may function as the first magnetic layer, too.
Other and further objects, features and advantages of the invention will appear more fully from the following description.